Solid electrolytic capacitor element and solid electrolytic capacitor

Abstract

The present invention is provided with: a positive electrode body; a dielectric layer formed on a surface of the positive electrode body; and a negative electrode part covering at least a portion of the dielectric layer. The negative electrode part is provided with a solid electrolyte layer that contains a conjugated polymer and that covers at least a portion of the dielectric layer. Provided is a solid electrolytic capacitor having excellent heat resistance by using a solid electrolytic capacitor element in which, in a Raman spectrum of the solid electrolyte layer, when a first peak attributable to CC stretching vibration and derived from the conjugated polymer is fitted by a Lorenz function, the full width at half maximum of the first peak is 35-80 cm-1.<sp / >

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolytic capacitor element and a solid electrolytic capacitor. [Background technology]

[0002] The solid electrolytic capacitor includes a solid electrolytic capacitor element, a resin outer casing or case that seals the solid electrolytic capacitor element, and external electrodes electrically connected to the solid electrolytic capacitor element. The solid electrolytic capacitor element includes an anode body, a dielectric layer formed on the surface of the anode body, and a cathode portion that covers at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer containing a conductive polymer component that covers at least a portion of the dielectric layer.

[0003] Patent Document 1 describes a solid electrolytic capacitor that is composed of an anode made of at least a valve metal, a dielectric film formed on the valve metal, and a solid electrolyte layer made of a conductive polymer formed on the dielectric film. ,stomach Patent Document 1 describes that the conductive polymer is formed by chemical polymerization or electrolytic polymerization. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-281410 Summary of the Invention

[0005] A solid electrolytic capacitor element according to a first aspect of the present disclosure includes an anode body, a dielectric layer formed on a surface of the anode body, and a cathode portion covering at least a portion of the dielectric layer. do. The cathode section covers at least a portion of the dielectric layer and includes a solid electrolyte layer containing a conjugated polymer. do. The Raman spectrum of the solid electrolyte layer shows the C originating from the conjugated polymer. =The first peak assigned to the C stretching vibration Has, In the Lorentz function of fitting obtained by The first peak Distribution shape Full width at half maximum is 35cm -1 More than 80cm -1 The following is the result.

[0006] A solid electrolytic capacitor element according to a second aspect of the present disclosure includes an anode body, a dielectric layer formed on a surface of the anode body, and a cathode portion covering at least a portion of the dielectric layer. do. The cathode section covers at least a portion of the dielectric layer and includes a solid electrolyte layer containing a conjugated polymer. do. Raman spectrum of the solid electrolyte layer teeth , C derived from the conjugated polymer = The first peak assigned to the C stretching vibration Has, In the Lorentz function of fitting obtained by The first peak Distribution shape The position is on the low wavenumber side from the reference position. Nisi It is soft, The shift amount of the position of the first peak from the reference position is 0.2% or more and 1% or less with respect to the wave number of the reference position. The reference position is a Raman spectrum of a solid electrolyte layer containing the conjugated polymer formed by bipolar electrolytic polymerization, and is determined by the C = The second peak is attributed to the C stretching vibration. The distribution shape of the second peak is In the Lorentz function of fitting obtained by .

[0007] A solid electrolytic capacitor according to a third aspect of the present disclosure includes at least one of the above solid electrolytic capacitor elements.

[0008] According to the present disclosure, it is possible to provide a solid electrolytic capacitor element and a solid electrolytic capacitor having excellent heat resistance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Before describing the embodiments, the problems in the prior art will be briefly described below. When air penetrates into a solid electrolytic capacitor, the moisture or oxygen contained in the air can cause degradation of the conductive polymer components (e.g., conjugated polymers, dopants) and reduce the conductivity of the solid electrolyte layer. Furthermore, if the orientation of the conjugated polymers in the solid electrolyte layer is low, cracks can form in the solid electrolyte layer when the solid electrolytic capacitor is exposed to high temperatures, making it easier for air to penetrate and resulting in degradation of the conductive polymer components. Degradation of the conductive polymer components is particularly pronounced in high-temperature environments. Depending on the application, solid electrolytic capacitors may be used in high-temperature environments. Furthermore, solid electrolytic capacitors are generally soldered to a substrate through a reflow process that exposes them to high temperatures. Therefore, there is a demand for solid electrolytic capacitor elements and solid electrolytic capacitors that suppress degradation of the conductive polymer components and have excellent heat resistance, even in high-temperature environments.

[0011] In view of the above, in the solid electrolytic capacitor element according to the first aspect of the present disclosure, the Raman spectrum of the solid electrolyte layer teeth , C derived from conjugated polymers = The peak (first peak) assigned to the C stretching vibration Has, The first peak when fitted with a Lorentzian function Distribution shape Full width at half maximum: 35cm -1 More than 80cm -1 Controlled as follows:

[0012] In the solid electrolytic capacitor element according to the second aspect of the present disclosure, in the Raman spectrum of the solid electrolyte layer, ,B When fitted with a Lenz function of First peak Distribution shape The position is on the low wavenumber side from the reference position Nisi Sudden , the shift amount of the position of the first peak from the reference position is 0.2% or more and 1% or less with respect to the wave number of the reference position.Here, the reference position is the C originating from the conjugated polymer in the Raman spectrum of the solid electrolyte layer containing the conjugated polymer formed by bipolar electrolytic polymerization. = Peak assigned to C stretching vibration (second peak) The distribution shape of the second peak is In the Lorentz function of fitting obtained by .

[0013] In the first aspect, high orientation of the conjugated polymer in the solid electrolyte layer can be ensured, resulting in a dense, rigid solid electrolyte layer with excellent film quality. Therefore, high conductivity of the solid electrolyte layer can be ensured. Furthermore, even when the solid electrolytic capacitor element is exposed to high temperatures, cracking in the solid electrolyte layer can be reduced, and degradation of the solid electrolyte layer is suppressed, thereby maintaining high conductivity and suppressing deterioration of capacitor performance. In the second aspect, the conjugated polymer in the solid electrolyte layer is energetically stabilized. Therefore, high conductivity of the solid electrolyte layer can be ensured. Even when the solid electrolytic capacitor element is exposed to high temperatures, oxidation reactions are unlikely to proceed, maintaining high conductivity and suppressing deterioration of capacitor performance. Therefore, in each of the first and second aspects, a solid electrolytic capacitor element and a solid electrolytic capacitor with excellent heat resistance can be obtained. Furthermore, the excellent heat resistance can be achieved, thereby improving the reliability of the solid electrolytic capacitor element and the solid electrolytic capacitor.

[0014] In the solid electrolytic capacitor elements of the first and second aspects, the solid electrolyte layer can be formed by three-electrode electropolymerization. Conventional electropolymerization is performed by a two-electrode system using an anode body with a dielectric layer formed on its surface as the anode, and two electrodes: this anode and a counter electrode. In contrast, three-electrode electropolymerization is performed by using an anode body with a dielectric layer formed on its surface as the anode, and three electrodes: this anode, a counter electrode, and a reference electrode. In three-electrode electropolymerization, the use of a reference electrode allows precise control of the anode potential without being affected by changes in the natural potential of the counter electrode. Therefore, in the case of a three-electrode system, the electropolymerization reaction is more precisely controlled than in a two-electrode system, resulting in increased orientation of the conjugated polymer formed by electropolymerization, improved crystallinity, and energetically stabilized conjugated polymers. Therefore, in the first aspect, the full width at half maximum of the first peak is 35 cm. -1 More than 80cm -1 or less (condition a). In the second aspect, the position of the first peak is on the lower wave number side than the position of the second peak (i.e., the reference position) for a solid electrolyte layer formed by bipolar electrolytic polymerization. Nisi Futo The shift amount is between 0.2% and 1% of the wave number at the reference position. (Condition b). In both the two-electrode and three-electrode types, the solid electrolyte layer can be formed by electrolytically polymerizing a conjugated polymer precursor on the surface of the dielectric layer, optionally in the presence of a dopant. In the second aspect, the conjugated polymer can be appropriately doped with the dopant, which reduces the conjugated polymer's reduction state, thereby preventing the oxidation reaction from proceeding and achieving high heat resistance.

[0015] The main component of the solid electrolyte layer is a conjugated polymer, and the Raman spectrum of the solid electrolyte layer shows C = The peak attributable to the C stretching vibration is the highest and most characteristic. In the solid electrolyte layer, when the orientation of the conjugated polymer increases or the energy state changes, the vibration state of the C C bond changes, and the C = At least one of the full width at half maximum and the position of the peak attributed to the C stretching vibration changes. =The orientation state or energy state of the conjugated polymer in the solid electrolyte layer can be determined based on at least one of the full width at half maximum and the peak position of the first peak attributed to the C stretching vibration.

[0016] In this specification, the Raman spectrum of the solid electrolyte layer is measured under the following conditions for a cross section of the solid electrolyte layer at a predetermined position of the solid electrolytic capacitor element. Raman spectrometer: NanoPhoton RamanFORCE PAV Diffraction grating: 600gr / cm Measurement wave number range: 0cm -1 More than 2500cm -1 below Temperature: 25℃ The wavelength of the irradiated laser light, the laser power density, and the exposure time are determined depending on the type of conjugated polymer. For example, when the conjugated polymer is polypyrrole, the irradiated laser light wavelength is 532 nm and the laser power density is 140 W / cm. 2 The exposure time was 75 seconds. When the conjugated polymer was poly(3,4-ethylenedioxythiophene) (PEDOT), the wavelength of the irradiated laser light was 785 nm and the laser power density was 660 W / cm. 2 and the exposure time is 60 seconds.

[0017] For Raman spectroscopy, samples prepared using the following procedure can be used. First, a solid electrolytic capacitor is embedded in a curable resin, which is then cured. The cured product is polished or cross-section polished to expose a cross section parallel to the thickness of the solid electrolyte layer and perpendicular to the length of the capacitor element. The cross section is taken at a position 0 to 0.05 from the end of the solid electrolyte layer opposite the anode lead, assuming that the length of the solid electrolyte layer in the direction parallel to the length of the capacitor element is 1. In this way, a sample for measurement (Sample A) is obtained. Raman spectroscopy is performed on an 8 μm × 8 μm area of ​​the cross section of the exposed solid electrolyte layer of Sample A, covering a portion of the solid electrolyte layer up to a depth of 100 nm (surface portion) from the surface, as well as portions formed within holes and depressions (sometimes called pits) on the surface of the anode body of the solid electrolyte layer. = The full width at half maximum and peak position of the peak attributed to the C stretching vibration were determined by averaging the measured values ​​for six 8 μm × 8 μm regions in the surface layer and 12 8 μm × 8 μm regions in the portion formed within the pits in the solid electrolyte layer.

[0018] The anode body typically has an anode lead portion having a first end and a cathode forming portion having a second end. Department or From the second end To the department The direction in which the anode body faces is referred to as the length direction of the anode body or capacitor element. The length of the solid electrolyte layer is the length in the direction parallel to the length direction of the capacitor element. Department or From the second end To the department The direction toward the first end is a direction parallel to the direction of a straight line connecting the center of the end face of the first end and the center of the end face of the second end.

[0019] Hereinafter, the solid electrolytic capacitor and solid electrolytic capacitor element (hereinafter sometimes simply referred to as capacitor element) of the present disclosure will be described in more detail with reference to the drawings as necessary.

[0020] [Solid electrolytic capacitor] A solid electrolytic capacitor includes one or more capacitor elements. At least one of the capacitor elements included in the solid electrolytic capacitor may have a solid electrolyte layer that satisfies at least one of conditions a and b. It is preferable that 50% or more (more preferably 75% or more) of the capacitor elements included in the solid electrolytic capacitor have a solid electrolyte layer that satisfies at least one of conditions a and b, and it is even more preferable that all of the capacitor elements have a solid electrolyte layer that satisfies at least one of conditions a and b.

[0021] (Capacitor element) (anode body) The anode body can contain a valve metal, an alloy containing a valve metal, a compound containing a valve metal, or the like. These materials can be used alone or in combination. Examples of preferred valve metals include aluminum, tantalum, niobium, and titanium. Anode bodies having a porous surface can be obtained by roughening the surface of a substrate containing a valve metal (such as a sheet-like (e.g., foil-like, plate-like) substrate) by etching or the like. Surface roughening can be achieved by etching or the like. The anode body can also be a compact or sintered body of particles containing a valve metal. The compact and sintered body each have a porous structure. The compact and sintered body each can be in the form of a sheet, a rectangular parallelepiped, a cube, or similar shapes.

[0022] The anode body typically has an anode lead portion and a cathode forming portion. The cathode portion is typically formed on the cathode forming portion of the anode body via a dielectric layer. An anode terminal is connected to the anode lead portion.

[0023] (dielectric layer) The dielectric layer is an insulating layer that functions as a dielectric and is formed so as to cover at least a portion of the surface of the anode body. The dielectric layer is formed by anodizing the valve metal on the surface of the anode body using a chemical conversion treatment or the like. The dielectric layer may be formed so as to cover at least a portion of the anode body. The dielectric layer is usually formed on the surface of the anode body. Because the dielectric layer is formed on the porous surface of the anode body, the surface of the dielectric layer has a fine uneven shape as described above.

[0024] The dielectric layer contains an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains Al2O3. However, the dielectric layer is not limited to these and may be any material that functions as a dielectric.

[0025] (cathode) The cathode section includes a solid electrolyte layer that covers at least a portion of the dielectric layer. The cathode section may further include a cathode extraction layer that covers at least a portion of the solid electrolyte layer. The cathode section is usually formed on at least a portion of the surface of the anode body via a dielectric layer. The solid electrolyte layer and the cathode extraction layer are described below.

[0026] (Solid electrolyte layer) The solid electrolyte layer is formed on the surface of the anode body via the dielectric layer so as to cover the dielectric layer. The solid electrolyte layer does not necessarily have to cover the entire dielectric layer (the entire surface), but only needs to cover at least a portion of the dielectric layer. The solid electrolyte layer constitutes at least a portion of the cathode part of the solid electrolytic capacitor.

[0027] The solid electrolyte layer usually contains a conductive polymer component, which contains at least a conjugated polymer and may further contain a dopant as needed.

[0028] (conjugated polymers) The conjugated polymer may be a known polymer used in electrolytic capacitors, such as a π-conjugated polymer. Examples of conjugated polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. The above polymers may contain at least one monomer unit constituting the basic skeleton. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (e.g., substituted products having a substituent group).

[0029] Among conjugated polymers, preferred are conjugated polymers containing monomer units corresponding to pyrrole compounds and conjugated polymers containing monomer units corresponding to thiophene compounds. Examples of pyrrole compounds include compounds having a pyrrole ring and capable of forming a repeating structure of the corresponding monomer units. Examples of thiophene compounds include compounds having a thiophene ring and capable of forming a repeating structure of the corresponding monomer units. These compounds can be linked at the 2- and 5-positions of the pyrrole or thiophene ring to form a repeating structure of the monomer units, thereby forming a polymer in which the π-electron cloud is spread throughout the molecule.

[0030] The pyrrole compound may have a substituent at, for example, at least one of the 3rd and 4th positions of the pyrrole ring. The thiophene compound may have a substituent at, for example, at least one of the 3rd and 4th positions of the thiophene ring. The substituent at the 3rd position and the substituent at the 4th position may be linked to form a ring fused to the pyrrole ring or the thiophene ring. Examples of the pyrrole compound include pyrrole which may have a substituent at, for example, at least one of the 3rd and 4th positions. Examples of the thiophene compound include thiophene which may have a substituent at, for example, at least one of the 3rd and 4th positions, alkylenedioxythiophene compounds (C thiophenes such as ethylenedioxythiophene compounds), etc. 2-4 Alkylenedioxythiophene compounds include those having a substituent in the alkylene group portion.

[0031] The substituents include alkyl groups (C such as methyl and ethyl groups) 1-4 alkyl groups, alkoxy groups (methoxy groups, ethoxy groups, etc.) 1-4 Alkoxy groups, hydroxy groups, hydroxyalkyl groups (hydroxy C groups such as hydroxymethyl groups) 1-4 Preferred examples of the thiophene compound include, but are not limited to, alkyl groups, etc. When the pyrrole compound and the thiophene compound each have two or more substituents, the substituents may be the same or different.

[0032] Among these, the use of a conjugated polymer containing at least a monomer unit corresponding to pyrrole, or a conjugated polymer (such as PEDOT) containing at least a monomer unit corresponding to a 3,4-ethylenedioxythiophene compound (such as 3,4-ethylenedioxythiophene (EDOT)), is preferred because it is easy to obtain high heat resistance and also to ensure higher conductivity of the solid electrolyte layer. A conjugated polymer containing at least a monomer unit corresponding to pyrrole may contain only a monomer unit corresponding to pyrrole, or may contain, in addition to the monomer unit, a monomer unit corresponding to a pyrrole compound other than pyrrole (such as a pyrrole having a substituent). A conjugated polymer containing at least a monomer unit corresponding to EDOT may contain only a monomer unit corresponding to EDOT, or may contain, in addition to the monomer unit, a monomer unit corresponding to a thiophene compound other than EDOT.

[0033] In a conjugated polymer containing a monomer unit corresponding to a pyrrole compound, the molar ratio of the monomer unit corresponding to the pyrrole compound (or pyrrole) is preferably 90 mol % or more, from the viewpoint of easily ensuring a higher capacitance. The molar ratio of the monomer unit corresponding to the pyrrole compound (or pyrrole) in the conjugated polymer is 100 mol % or less. The conjugated polymer may be composed only of a repeating structure of the monomer unit corresponding to the pyrrole compound (or pyrrole).

[0034] In a conjugated polymer containing a monomer unit corresponding to a thiophene compound, the molar ratio of the monomer unit corresponding to the thiophene compound (or EDOT) is preferably 90 mol% or more, from the viewpoint of easily ensuring a higher capacitance. The molar ratio of the monomer unit corresponding to the thiophene compound (or EDOT) in the conjugated polymer is 100 mol% or less. The conjugated polymer may be composed only of a repeating structure of the monomer unit corresponding to the thiophene compound (or EDOT).

[0035] The conjugated polymer may be used alone or in combination of two or more kinds.

[0036] The weight average molecular weight (Mw) of the conjugated polymer is not particularly limited, but is, for example, 1,000 or more and 1,000,000 or less.

[0037] In this specification, the weight-average molecular weight (Mw) is a value calculated as polystyrene measured by gel permeation chromatography (GPC), which is usually performed using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as the mobile phase.

[0038] (dopant) As the dopant, for example, at least one selected from the group consisting of anions and polyanions is used.

[0039] Examples of anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, carboxylate ions, etc. Examples of dopants that generate sulfonate ions include p-toluenesulfonic acid and naphthalenesulfonic acid.

[0040] Examples of polyanions include polymer anions. The solid electrolyte layer may contain, for example, a conjugated polymer containing a monomer unit corresponding to a thiophene compound and a polymer anion. When the solid electrolytic capacitor contains a polymer anion, undoping is less likely to occur even when the solid electrolytic capacitor element is exposed to high temperatures, resulting in higher heat resistance.

[0041] Examples of polymer anions include polymers having multiple anionic groups. Such polymers include those containing monomer units having anionic groups. Examples of the anionic groups include sulfonic acid groups and carboxyl groups.

[0042] In the solid electrolyte layer, the anionic group of the dopant may be contained in a free form, an anion form, or a salt form, or may be contained in a form bound to or interacting with the conjugated polymer. In this specification, all of these forms may be simply referred to as an "anionic group," "sulfonic acid group," "carboxy group," or the like.

[0043] Examples of polymer anions having a carboxy group include, but are not limited to, polyacrylic acid, polymethacrylic acid, and copolymers using at least one of acrylic acid and methacrylic acid.

[0044] Specific examples of polymer anions having sulfonic acid groups include, but are not limited to, polymeric polysulfonic acids such as polyvinyl sulfonic acid, polystyrene sulfonic acid (including copolymers and substituted products having substituents), polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acids (such as aromatic polyester sulfonic acids), and phenolsulfonic acid novolac resins.

[0045] The amount of the dopant contained in the solid electrolyte layer is, for example, 10 to 1000 parts by mass, or may be 20 to 500 parts by mass, or 50 to 200 parts by mass, relative to 100 parts by mass of the conjugated polymer.

[0046] (Raman spectrum) In the Raman spectrum of the solid electrolyte layer, the full width at half maximum of the first peak is, for example, 80 cm -1 This results in a high degree of orientation of the conjugated polymer, resulting in a solid electrolyte layer with excellent film quality, ensuring high heat resistance of the solid electrolytic capacitor. The full width at half maximum of the first peak is 35 cm -1 In this case, a solid electrolyte layer can be easily formed. From the viewpoint of obtaining higher orientation and higher heat resistance, the full width at half maximum of the first peak is set to 50 cm. -1 It may be more than 55cm -1 or above or 58cm -1 It may be more than that.

[0047] In the Raman spectrum of the solid electrolyte layer, the position of the first peak shifts to the lower wavenumber side from the reference position when the solid electrolyte layer is formed by bipolar electrolytic polymerization. The amount of shift is usually With respect to the wave number of the reference position The shift amount is 0.2% or more, preferably 0.25% or more or 0.3% or more. When the shift amount is within this range, the conjugated polymer is in an energetically stabilized state in the solid electrolyte layer, making it difficult for an oxidation reaction to proceed. For example, the conjugated polymer is easily doped with a dopant to an appropriate degree, which reduces the conjugated polymer from being in a reduced state. Therefore, high heat resistance is obtained. The shift amount is usually With respect to the wave number of the reference position The shift amount is 1% or less, and may be 0.7% or less, or 0.51% or less. When the shift amount is within this range, the conjugated polymer is easily doped with the dopant to an appropriate degree, thereby preventing excessive decomposition of the dopant contained in the solid electrolyte layer. Therefore, high heat resistance is obtained. The lower limit and upper limit of the shift amount can be combined arbitrarily.

[0048] For example, when the conjugated polymer contains at least a monomer unit corresponding to pyrrole, the position of the first peak is 1566 cm -1 Over 1578cm -1 Preferably, it is 1570 cm or less. -1 Over 1577cm -1 The following is more preferable: When the conjugated polymer contains at least a monomer unit corresponding to EDOT, the position of the first peak is 1423 cm -1 Over 1435cm -1 Preferably, it is 1429 cm or less. -1 Over 1434cm -1 It is more preferable that the temperature is not more than 100°C. In these cases, higher heat resistance of the solid electrolytic capacitor element can be ensured.

[0049] (others) The solid electrolyte layer may further contain, as necessary, at least one selected from the group consisting of known additives and known conductive materials other than the conductive polymer component, such as at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0050] The solid electrolyte layer may be a single layer or may be composed of multiple layers. For example, the solid electrolyte layer may be composed of a first solid electrolyte layer covering at least a portion of the dielectric layer and a second solid electrolyte layer covering at least a portion of the first solid electrolyte layer. The types, compositions, and contents of conductive polymer components, additives, etc. contained in each layer may be different or the same.

[0051] A layer for enhancing adhesion (for example, a precoat layer made of a conductive material) may be interposed between the dielectric layer and the solid electrolyte layer.

[0052] (Method for forming a solid electrolyte layer) The solid electrolyte layer can be formed on the surface of the dielectric layer by electropolymerizing a conjugated polymer precursor in the presence of a dopant, if necessary, in a three-electrode system. For example, electropolymerization is performed while the cathode-forming portion of the anode body, on which the dielectric layer is formed, is immersed in a liquid mixture containing the conjugated polymer precursor and, if necessary, the dopant. This electropolymerization can improve the orientation of the conjugated polymer. Furthermore, the dopant is appropriately doped, energetically stabilizing the conjugated polymer. This ensures high heat resistance of the capacitor element.

[0053] Examples of precursors of conjugated polymers include raw material monomers of conjugated polymers, oligomers and prepolymers in which multiple molecular chains of raw material monomers are linked together. One type of precursor may be used, or two or more types may be used in combination. From the viewpoint of easily obtaining higher orientation of the conjugated polymer, it is preferable to use at least one type (particularly a monomer) selected from the group consisting of monomers and oligomers as the precursor.

[0054] The liquid mixture usually contains a solvent, such as water, an organic solvent, or a mixed solvent of water and an organic solvent (such as a water-soluble organic solvent).

[0055] If dopants, other conductive materials, additives, etc. are used, they may be added to the liquid mixture.

[0056] The liquid component may contain an oxidizing agent, if necessary. The oxidizing agent may be applied to the anode body before or after contacting the liquid mixture with the anode body on which the dielectric layer has been formed. Examples of such oxidizing agents include sulfates, sulfonic acids, and their salts. The oxidizing agents may be used singly or in combination of two or more. Examples of sulfates include salts of metals with sulfuric acid, such as ferric sulfate and sodium persulfate, and salts of sulfates such as persulfates. Examples of metals constituting the salts include alkali metals (sodium, potassium, etc.), iron, copper, chromium, and zinc. Sulfonic acids and their salts function not only as oxidizing agents but also as dopants. Examples of sulfonic acids and their salts include low-molecular-weight sulfonic acids and their salts, as exemplified for other dopants.

[0057] The pH of the liquid mixture is, for example, 0.5 to 2.5, preferably 0.5 to 2 or 1 to 2. When the pH of the liquid mixture is in this range, oxygen generation during electrolytic polymerization can be suppressed, making it easier to obtain a solid electrolyte layer with excellent film quality. The pH of the liquid mixture can be adjusted, for example, by adjusting the content of the dopant or the content of the oxidizing agent in the liquid mixture.

[0058] The three-electrode electropolymerization is carried out by immersing an anode body, a counter electrode, and a reference electrode in the liquid mixture. The counter electrode may be, but is not limited to, a Ti electrode. The reference electrode may be a silver / silver chloride electrode (Ag / Ag + ) is preferably used.

[0059] In electropolymerization, the voltage (polymerization voltage) applied to the anode body is, for example, 0.6 V or more and 1.5 V or less, or may be 0.7 V or more and 1 V or less, or 0.7 V or more and 0.9 V or less. By performing electropolymerization in a three-electrode system, electropolymerization can be performed at a relatively low polymerization voltage, and the polymerization reaction can be precisely controlled. This makes it possible to further improve the orientation of the conjugated polymer. In addition, it is possible to dope the dopant appropriately. The polymerization voltage is set by using a reference electrode (silver / silver chloride electrode (Ag / Ag+ )). In electropolymerization, a power supply (such as a power supply tape) is electrically connected to the anode lead, and a voltage is applied to the anode via the power supply. The potential of the anode is the potential of the power supply electrically connected to the anode.

[0060] The temperature at which electropolymerization is carried out is, for example, 5°C or higher and 60°C or lower, and may be 15°C or higher and 35°C or lower.

[0061] (Cathode extraction layer) The cathode extraction layer may include at least a first layer that is in contact with the solid electrolyte layer and covers at least a portion of the solid electrolyte layer, and may also include a first layer and a second layer that covers the first layer. Examples of the first layer include a layer containing conductive particles and metal foil. Examples of the conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may be formed of a first layer containing conductive carbon (also referred to as a carbon layer) and a second layer containing metal powder or metal foil. When metal foil is used as the first layer, the cathode extraction layer may be formed of this metal foil.

[0062] Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0063] The second layer containing metal powder can be formed, for example, by laminating a composition containing metal powder on the surface of the first layer. Examples of such second layers include metal paste layers formed using a composition containing metal powder such as silver particles and a resin (binder resin). While thermoplastic resins can be used as the resin, it is preferable to use thermosetting resins such as imide resins and epoxy resins.

[0064] When a metal foil is used as the first layer, the type of metal is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a nonmetal different from the metal constituting the metal foil. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon (e.g., conductive carbon).

[0065] The coating of the dissimilar metal or non-metal (for example, conductive carbon) may be the first layer, and the metal foil may be the second layer.

[0066] (separator) When a metal foil is used for the cathode extraction layer, a separator may be disposed between the metal foil and the anode foil. The separator is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).

[0067] (others) The solid electrolytic capacitor may be a wound type, a chip type, or a laminate type. For example, the solid electrolytic capacitor may include a laminate of two or more capacitor elements. The configuration of the capacitor elements may be selected depending on the type of solid electrolytic capacitor.

[0068] In the capacitor element, one end of a cathode terminal is electrically connected to the cathode extraction layer. The cathode terminal is bonded to the cathode extraction layer, for example, by applying a conductive adhesive to the cathode extraction layer and bonding the cathode terminal to the cathode extraction layer via the conductive adhesive. One end of the anode terminal is electrically connected to the anode body. The other end of the anode terminal and the other end of the cathode terminal are each extended from the resin exterior body or the case. The other end of each terminal exposed from the resin exterior body or the case is used for soldering to a substrate on which the solid electrolytic capacitor is to be mounted, for example.

[0069] The capacitor element is sealed using a resin outer casing or case. For example, the capacitor element and the resin material of the outer casing (e.g., uncured thermosetting resin and filler) may be placed in a mold, and the capacitor element may be sealed in the resin outer casing by transfer molding, compression molding, or the like. At this time, the other end portions of the anode terminal and cathode terminal connected to the anode lead drawn from the capacitor element are exposed from the mold. Alternatively, the capacitor element may be placed in a bottomed case so that the other end portions of the anode terminal and cathode terminal are positioned on the opening side of the bottomed case, and the opening of the bottomed case may be sealed with a sealant to form a solid electrolytic capacitor.

[0070] Fig. 1 is a cross-sectional view schematically illustrating the structure of a solid electrolytic capacitor according to an embodiment of the present disclosure. As shown in Fig. 1, solid electrolytic capacitor 1 includes a capacitor element 2, a resin outer casing 3 that seals capacitor element 2, and an anode terminal 4 and a cathode terminal 5, at least a portion of which is exposed to the outside of resin outer casing 3. Anode terminal 4 and cathode terminal 5 may be made of a metal such as copper or a copper alloy. Resin outer casing 3 has a substantially rectangular parallelepiped outer shape, and solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0071] The capacitor element 2 includes an anode body 6, a dielectric layer 7 covering the anode body 6, and a cathode portion 8 covering the dielectric layer 7. The cathode portion 8 includes a solid electrolyte layer 9 covering the dielectric layer 7, and a cathode extraction layer 10 covering the solid electrolyte layer 9. In the illustrated example, the solid electrolyte layer 9 includes a conjugated polymer.

[0072] The anode body 6 includes a region facing the cathode portion 8 and a region not facing the cathode portion 8. Of the region of the anode body 6 not facing the cathode portion 8, an insulating separator 13 is formed in a strip-like shape on the surface of the anode body 6 in a portion adjacent to the cathode portion 8, thereby restricting contact between the cathode portion 8 and the anode body 6. Of the region of the anode body 6 not facing the cathode portion 8, another part is electrically connected to the anode terminal 4 by welding. The cathode terminal 5 is electrically connected to the cathode portion 8 via an adhesive layer 14 formed of a conductive adhesive.

[0073] [Example] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0074] <Solid electrolytic capacitors A1 to A4> Solid electrolytic capacitors 1 (solid electrolytic capacitors A1 to A4) shown in FIG. 1 were fabricated in the following manner, and their characteristics were evaluated.

[0075] (1) Preparation of anode body 6 Anode body 6 was produced by roughening both surfaces of an aluminum foil (thickness: 100 μm) used as a substrate by etching.

[0076] (2) Formation of dielectric layer 7 The cathode forming portion of the anode body 6 was immersed in the chemical conversion solution, and a direct current voltage of 70 V was applied for 20 minutes to form a dielectric layer 7 containing aluminum oxide.

[0077] (3) Formation of solid electrolyte layer 9 An insulating resist tape was attached to anode body 6 on which dielectric layer 7 was formed, between a region where a solid electrolyte layer was to be formed and a region where a solid electrolyte layer was not to be formed, thereby forming separation portion 13. Anode body 6 on which separation portion 13 was formed was immersed in a liquid composition containing a conductive material, taken out, and dried to form a precoat layer (not shown).

[0078] A polymerization solution containing pyrrole (a monomer for a conjugated polymer), naphthalenesulfonic acid (a dopant), and water was prepared. The pH of the polymerization solution was adjusted by adjusting the amount of naphthalenesulfonic acid added, as shown in Table 1. Using the resulting polymerization solution, electropolymerization was performed using a three-electrode system. More specifically, an anode body 6 on which a precoat layer had been formed, a counter electrode, and a reference electrode (a silver / silver chloride reference electrode) were immersed in the polymerization solution. A voltage was applied to the anode body 6 so that the potential of the anode body 6 relative to the reference electrode was the polymerization voltage value shown in Table 1, and electropolymerization was performed at 25°C to form a solid electrolyte layer 9.

[0079] (4) Formation of the Cathode Extraction Layer 10 Anode body 6 obtained in (3) above was immersed in a dispersion liquid in which graphite particles were dispersed in water, and then removed from the dispersion liquid and dried, thereby forming carbon layer 11 at least on the surface of solid electrolyte layer 9. Drying was carried out at 130 to 180°C for 10 to 30 minutes.

[0080] Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of carbon layer 11, and the binder resin was cured by heating at 150 to 200°C for 10 to 60 minutes to form metal paste layer 12. In this way, cathode extraction layer 10 composed of carbon layer 11 and metal paste layer 12 was formed, and cathode part 8 composed of solid electrolyte layer 9 and cathode extraction layer 10 was formed. Capacitor element 2 was fabricated in the manner described above.

[0081] (5) Assembly of solid electrolytic capacitors Cathode part 8 of capacitor element 2 obtained in (4) above was joined to one end of cathode terminal 5 with adhesive layer 14 of a conductive adhesive. One end of anode body 6 protruding from capacitor element 2 was joined to one end of anode terminal 4 by laser welding.

[0082] Next, a resin outer casing 3 made of insulating resin was formed around the capacitor element 2 by molding. At this time, the other end of the anode terminal 4 and the other end of the cathode terminal 5 were left pulled out from the resin outer casing 3.

[0083] In this way, solid electrolytic capacitors 1 (A1 to A5) were completed. In the same manner as above, a total of 20 of each solid electrolytic capacitor were produced.

[0084] <Solid electrolytic capacitor A5> 3,4-ethylenedioxythiophene monomer and the polymer anion polystyrene sulfonate (PSS, Mw: 160 × 10 3) was dissolved in ion-exchanged water to prepare a mixed solution. Iron (III) sulfate (oxidant) dissolved in ion-exchanged water was added to the mixed solution while stirring, to prepare a polymerization solution. A total of 20 solid electrolytic capacitors A5 were fabricated in the same manner as solid electrolytic capacitors A1 to A4, except that the obtained polymerization solution was used.

[0085] <Solid electrolytic capacitor B1> A total of 20 solid electrolytic capacitors B1 were formed in the same manner as solid electrolytic capacitors A1 to A4, except that electrolytic polymerization was performed using a two-electrode system. In the electrolytic polymerization, the anode body on which the precoat layer was formed and a Ti electrode as a counter electrode were immersed in a polymerization solution, and a voltage was applied to the anode body so that the potential of the anode body relative to the silver / silver chloride reference electrode became the polymerization voltage value shown in Table 1, thereby forming a solid electrolyte layer.

[0086] <Solid electrolytic capacitor B2> A total of 20 solid electrolytic capacitors B2 were formed in the same manner as solid electrolytic capacitor A5, except that electrolytic polymerization was performed using a two-electrode system. For electrolytic polymerization, the anode body on which the precoat layer was formed and a Ti electrode as a counter electrode were immersed in a polymerization solution, and a voltage was applied to the anode body so that the potential of the anode body relative to the silver / silver chloride reference electrode became the polymerization voltage value shown in Table 1, thereby forming a solid electrolyte layer.

[0087] [evaluation] The solid electrolytic capacitors were evaluated as follows.

[0088] (a) Raman spectrum measurement of the solid electrolyte layer The Raman spectrum of the cross section of the solid electrolyte layer of the capacitor element taken out of the solid electrolytic capacitor was measured using the procedure described above. In the Raman spectrum of the solid electrolyte layer of solid electrolytic capacitor B1, C derived from polypyrrole was observed. = The peak (second peak) assigned to the C stretching vibration is 1582 cm -1 In the Raman spectrum of the solid electrolyte layer of solid electrolytic capacitor B2, C originating from PEDOT was observed. =The peak (second peak) assigned to the C stretching vibration is 1438 cm -1 In the Raman spectrum of the solid electrolyte layer of the capacitor element taken out of each solid electrolytic capacitor, the full width at half maximum of the first peak derived from polypyrrole or PEDOT was determined, and the shift amount from the position of the second peak (reference position) was also determined. The shift amount is the actual shift amount (cm) of the first peak from the reference position when the wave number at the reference position is set to 100%. -1 The results were evaluated as a percentage of the total.

[0089] (b) Capacitance The initial capacitance (μF) of each solid electrolytic capacitor was measured at a frequency of 120 Hz using a four-terminal LCR meter in an environment of 20°C, and the average value for the 20 solid electrolytic capacitors was calculated.

[0090] Next, an accelerated test was performed by applying the rated voltage to the solid electrolytic capacitors for 2,000 hours in a 145°C environment. The capacitance after the accelerated test was then measured in a 20°C environment using the same procedure as for the initial capacitance, and the average value for 20 solid electrolytic capacitors was calculated. The capacitance change rate was calculated by subtracting the initial capacitance from the capacitance after the accelerated test, and was expressed as a ratio with the initial capacitance set to 100%. The capacitance change rate was a negative value, and a smaller value indicates lower heat resistance.

[0091] The evaluation results are shown in Table 1. B1 and B2 are comparative examples.

[0092] [Table 1] [Industrial Applicability]

[0093] According to the present disclosure, a solid electrolytic capacitor element and a solid electrolytic capacitor having excellent heat resistance are provided, and therefore the solid electrolytic capacitor element and the solid electrolytic capacitor can be used in a variety of applications requiring high reliability. [Explanation of symbols]

[0094] 1: solid electrolytic capacitor, 2: capacitor element, 3: resin outer casing, 4: anode terminal, 5: cathode terminal, 6: anode body, 7: dielectric layer, 8: cathode part, 9: solid electrolyte layer, 10: cathode lead layer, 11: carbon layer, 12: metal paste layer, 13: separation part, 14: adhesive layer

Claims

1. an anode body, a dielectric layer formed on a surface of the anode body, and a cathode portion covering at least a portion of the dielectric layer, the cathode section includes a solid electrolyte layer that covers at least a portion of the dielectric layer and includes a conjugated polymer; The Raman spectrum of the solid electrolyte layer has a first peak attributed to the C═C stretching vibration derived from the conjugated polymer, and the full width at half maximum of the distribution shape of the first peak obtained by fitting with a Lorentz function is 35 cm －１ 80cm or more －１ A solid electrolytic capacitor element as follows:

2. the position of the first peak is shifted to a lower wavenumber side from the reference position, a shift amount of the position of the first peak from the reference position is 0.2% or more and 1% or less with respect to the wave number of the reference position, 2. The solid electrolytic capacitor element according to claim 1, wherein the reference position is a position of a distribution shape of a second peak attributed to a C=C stretching vibration derived from the conjugated polymer in a Raman spectrum of a solid electrolyte layer containing the conjugated polymer formed by bipolar electropolymerization, and the distribution shape of the second peak is obtained by fitting with a Lorentz function.

3. an anode body, a dielectric layer formed on a surface of the anode body, and a cathode portion covering at least a portion of the dielectric layer, the cathode section includes a solid electrolyte layer that covers at least a portion of the dielectric layer and includes a conjugated polymer; the Raman spectrum of the solid electrolyte layer has a first peak attributed to a C═C stretching vibration derived from the conjugated polymer, and the position of the distribution shape of the first peak obtained by fitting with a Lorentz function is shifted to a lower wavenumber side from a reference position; a shift amount of the position of the first peak from the reference position is 0.2% or more and 1% or less with respect to the wave number of the reference position, a solid electrolytic capacitor element, wherein the reference position is a position of a distribution shape of a second peak attributable to a C═C stretching vibration derived from a conjugated polymer in a Raman spectrum of a solid electrolyte layer containing the conjugated polymer formed by bipolar electropolymerization, and the distribution shape of the second peak is obtained by fitting with a Lorentz function.

4. the conjugated polymer contains at least a monomer unit corresponding to pyrrole, The reference position is 1582 cm －１ 4. The solid electrolytic capacitor element according to claim 2, wherein

5. the conjugated polymer contains at least a monomer unit corresponding to 3,4-ethylenedioxythiophene; The reference position is 1438 cm －１ 4. The solid electrolytic capacitor element according to claim 2, wherein

6. the conjugated polymer contains at least a monomer unit corresponding to pyrrole, The position of the first peak is 1566 cm －１ 1578cm or more －１ 2. The solid electrolytic capacitor element according to claim 1, wherein:

7. the conjugated polymer contains at least a monomer unit corresponding to 3,4-ethylenedioxythiophene; The position of the first peak is 1423 cm －１ 1435cm or more －１ 2. The solid electrolytic capacitor element according to claim 1, wherein:

8. The solid electrolytic capacitor element according to claim 5 , wherein the solid electrolyte layer further contains a polymer anion.

9. A solid electrolytic capacitor comprising at least one solid electrolytic capacitor element according to any one of claims 1 to 8.

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